If a civilian withdrawal had begun earlier in an orderly way, BEFORE Biden removed the last troops, there would have been no mad rush to the gates, people also could have flown out through Baghram air base and there would have been no need for the additional US troops because the Afghan army would not have fallen
There was no indication in April when the announcement was made that the Afghan Army was not going to live up to the expectations.
There was no way to secure Baghgram, Kabul's airport, and the Embassy with 2500 troops. Biden had to add at least 2500 more to the troop level he was left by the previous President just to secure Kabul's airport.